150W Is it good?

[millwood]

Originally posted by Tube_Dude
About the VAS current value indeterminated...
The current in the LTP is defined by the CCS and cause a voltage drop in the colector resistor...this voltage drop define the voltage of the base of the VAS transistor...and that voltage define de current in the VAS by action of the emiter resistor of the VAS.
So i don't see any reason for this current to be indeterminated.
This kind of VAS biasing is a typical one!

well, try to calculate the current on T7 or T7, .

sreten is right on that one.

[Tube_Dude]

Originally posted by sreten


Well the way I see it the VAS current affects the current sharing
in the LTP's or vice versa, neither the current sharing or VAS
current is fixed as I see it, which is why I said indeterminate.

sreten.

No...the VAS current doesn't affect the current in th LTP...it's the oposite in fact, the current in the LTP define the current in the VAS.Via the voltage drop in the colector resistor of the LTP

[millwood]

Originally posted by Tube_Dude


No...the VAS current doesn't affect the current in th LTP...

yes, it does. end of the day, the voltage drop off the collector resistor (680ohm for T2) has to be the same as the voltage drop on the base of T7 (Vbe of T7 + voltage drop off R15/47ohm).

Now, try to figure out how much that is,

[Tube_Dude]

Originally posted by millwood



well, try to calculate the current on T7 or T7, .

sreten is right on that one.

Is very easy!!! if yo tell me the voltage drop at the LED of the CCS...actually is this voltage that define all the operation points...

[millwood]

Originally posted by Tube_Dude


Is very easy!!! if yo tell me the voltage drop at the LED of the CCS...actually is this voltage that define all the operation points...

pick a number. mine would be 2.8v.

[Tube_Dude]

Originally posted by millwood



pick a number. mine would be 2.8v.

Well i do your home work!!

Current in the LTP tail 4,6 mA.
2,3 mA in each arm of the LTP.
Voltage drop in the colector resistor of the LTP 1,6 V
Current in the VAS 21 mA .(With 47 Ohms...and 10,5 mA with 100 Ohms)
That's all folks!

[millwood]

Originally posted by Tube_Dude
Current in the LTP tail 4,6 mA.
2,3 mA in each arm of the LTP.

what makes you think the current in each arm is just 1/2 of the tail current? if that's the case, why do we need current mirrors?

[Tube_Dude]

Originally posted by millwood



what makes you think the current in each arm is just 1/2 of the tail current? if that's the case, why do we need current mirrors?

Basic electronics!!!

[millwood]

Originally posted by Tube_Dude


Basic electronics!!!

it suffices to say that unless that "electronics" is out of this world, you cannot assume that the two arms will split the tail current evenly.

In a typical ltp (with resistors), the current in each arm is determined by the VAS stage. So you would know the voltage drop off R15, plus the Vbe of T7. then you can calculate the current through the 680ohm resistor for T2.

In this case, there is no way to determine the voltage drop off the 680ohm resistor, nor the idle current for the VAS.

not until you use "out-of-this-world" laws of physics,

edit: tube-dude, you may wan tto look into this thread to better understand the issue here.

Unstable VAS current in amp from Slone book

[ChocoHolic]

Hi folks!
I think Dude is right.
Depending on 47 Ohms or 100 Ohms I also end
up in about 10mA (100 Ohms) or 20mA (47 Ohms).

With respect to the transitortype of T7 2N5401 and its complementary,
I think 100 Ohms are enough. Don't go for BBQ....
The lower current does also match with the fact the there is
a tripple darlington for current amplification.

Cheers
Markus